Large eddy simulation is performed to investigate the mechanism of the vertical sorting of sediments under sheet-flow regime particularly from a viewpoint of interacting between eddies and sediment based on the solid-liquid multiphase turbulent flow model. The agreements between experimental results and numerical results are reasonable with choosing the model parameters in the distinct element method for simulating movable bed. The developing process of the vertical sorting is discussed through the distribution of the phase-dependent turbulent energy production.